U.S. Pat. No. 3,894,154 to Graff et al discloses a center-filled chewing gum which includes as a liquid fill an aqueous solution having a dissolved solids portion, and a humectant for retarding increase in viscosity of the center fill. The dissolved solids portion may include invert sugar, sucrose and glucose, while the humectant is glycerine.
British Pat. No. 1,469,031 discloses a center-filled chewing gum similar to that disclosed in U.S. Pat. No. 3,894,154 except that in addition to glycerine, the humectant may be polylimonene, sorbitol solution, lecithin, dextrose, gum arabic, glyceryl monostearate, polyethylene glycol or propylene glycol.
U.S. Pat. No. 4,156,740 to Glass et al discloses a center-filled chewing gum which includes in both the chewing gum shell and the center fill A. from 0.4 to 1 part by weight of a natural or synthetic gum, namely, carboxymethyl cellulose, pectin, propylene glycol, alginates, agar or gum tragacanth; B. from 50 to 84 parts by weight of a glycerin humectant; and C. from 15 to 49.6 parts by weight of an additional water-miscible humectant ingredient which is sorbitol solution or sorbitol solution and propylene glycol.